Buck-boost converter

Bidirectional half-bridge: port 1 is the switch node (add a series inductor); fire_p drives the low-side switch, stepping up from port 1 to port 2, and fire_n the high-side switch, stepping down from port 2 to port 1.

  • Boolean
  • electrical
  • Modelica Standard Library
  • 6 ports
  • 2 parameters
BlockBuck-boost converterKindbuckBoostConverterLibraryConverters

Description

A bidirectional half-bridge chopper: two transistors, each with an antiparallel diode. The low-side switch sits across port 1 (dc_p1 to dc_n1); the high-side switch conducts from dc_p2 to dc_p1. dc_n1 and dc_n2 are the same node.

Port 1 is the switch node and needs an external series inductor; port 2 is the high-voltage bus. Switching fire_p boosts power from port 1 to port 2; switching fire_n bucks power from port 2 to port 1.

Example

DC-DC converters Buck, boost, and bidirectional half-bridge converters switching at 10 kHz with 50 % duty.

Duty A 0.5PWM 10 kHzC A 100 µFLoad A 10 Ωv out A24 VGround (buck)BuckL 1 mHDuty B 0.5PWM 10 kHz (boost)C B 100 µFLoad B 50 Ωv out B12 VGround (boost)L 1 mH (boost)BoostDuty C 0.5PWM 10 kHz (half-bridge)C C 100 µFLoad C 50 Ωv out C12 V (half-bridge)Ground (half-bridge)L 1 mH (half-bridge)Half-bridge
In Gradara, select a Buck-boost converter block and press F1, then choose Open example. It opens as a new model in My models, ready to run.

Also in this example:DC voltageVoltage sensorConstantGroundResistorCapacitorInductorBuck converterBoost converterPWM generator

Ports

Inputs 2

  • lofire_pBoolean

    Gate of the low-side transistor (dc_p1 to dc_n1). Its duty cycle sets the step-up ratio.

  • hifire_nBoolean

    Gate of the high-side transistor (dc_p2 to dc_p1). Its duty cycle sets the step-down ratio.

Conserving terminals 4

  • 1+dc_p1electrical

    Low-voltage side positive terminal: the switch node. Connect it through the inductor.

  • 1−dc_n1electrical

    Low-voltage side negative terminal, connected internally to dc_n2.

  • 2+dc_p2electrical

    High-voltage side positive terminal.

  • 2−dc_n2electrical

    High-voltage side negative terminal, connected internally to dc_n1.

Parameters

  • Transistor on resistanceRonTransistor0.00001 Ω

    ≥ 0

    On resistance of each transistor, in ohms. 0 or more.

  • Diode on resistanceRonDiode0.00001 Ω

    ≥ 0

    On resistance of each freewheeling diode, in ohms. 0 or more.

Equations

Modelica
Complementary gating, fire_p duty cycle d, continuous conduction: mean(v1) ≈ (1 − d) · v2
The sign of the inductor current sets the direction of power flow.

Implementation

Modelica Standard Library 4.1.0Modelica.Electrical.PowerConverters.DCDC.ChopperBuckBoost
MSL documentation

Assumptions and limitations

  • Ideal switches: transistors are GTO-type switches that conduct only forward, and diodes switch at 0 V. Off conductance is fixed at 10 µS and knee voltages at 0 V. No switching times, reverse recovery, or conduction voltage drop beyond the on resistance.
  • It cannot produce v1 > v2: it is not a four-switch non-inverting buck-boost.
  • fire_p and fire_n both true shorts port 2. No dead time is inserted.

Tips

  • Drive fire_p from fire and fire_n from notFire of one PWM generator.

See also

Select a block in Gradara and press F1 to open its page offline.